ADT specifying whether the schema is the self-describing schema for all rows returned by the query, or whether the schema should be attached to each of the returned rows.
ADT specifying what amount of rows are expecting from DB
Box all returned rows - i.
More that 1 rows are expected 0 rows will throw an error
Always successful
Either one or zero rows is expected.
Attached Schema URI to each returned row - so e.
Exactly one row is expected.